For all kinds for reasons including speed of access, ease of set-up and generally not putting all eggs in one basket, I'd always put my music collection on a different device to my system/main computer back-up. And no, nothing whatsoever to do with sound quality, before anyone starts!

I bought a tc as a nas. It simply does not work. It is a great tool for backups but will not work as a nas. If you search around on the forum you will find my post somewhere. I just use it for backups and as a 2nd wifi router on my system now. I have bought a nas but don't know how to work it... Still sitting in its box. I bought it from currys/pc world and the assistant told me I would be able to access anything on the tc from my iPad/apple tv. Simply a lot of rubbish. The tc is not designed as a nas. Only backups.

Look elsewhere, I haven't checked but I'm prepared to bet you'll get more storage for less money. I use a Lacie 3TB NAS for both music storage, video storage and as a Time Machine for three Macs. No serious problems to report so far, though I've made a remote backup of all my music on another 2TB HDD to avoid the eggs-in-one-basket scenario. Seems a sensible thing to do, considering how long it took me to rip the things (months).